Update subscriptions.json (#10709)

Author: navysingla

specification/subscription/resource-manager/Microsoft.Subscription/stable/2020-09-01/subscriptions.json

@@ -436,11 +436,6 @@
     },
     "PutAliasRequestProperties": {
       "description": "Put subscription properties.",
-      "required": [
-        "displayName",
-        "workload",
-        "billingScope"
-      ],
       "properties": {
         "displayName": {
           "description": "The friendly name of the subscription.",